Flying-wing aerodynamic stability in XFLR5
A multi-stage aerodynamic and stability analysis of flying wing configurations using XFLR5, evaluating the impact of geometry and centre of gravity position on longitudinal static stability — the defining problem of a tailless aircraft.
Method and results
A rectangular wing based on a cambered NACA 1410 airfoil was analysed first. This demonstrated that variations in centre of gravity do not affect the lift or efficiency polars but significantly alter pitching moment behaviour, leading to inherently unstable configurations.
This was then compared with a negatively cambered Eppler 186 airfoil, identifying a neutral point at x_CG = 25 mm and establishing stable configurations for forward CG positions. The comparison highlights the critical role of airfoil selection in achieving self-stability — a reflexed section changes the sign of the moment contribution outright.
/assets/img/projects/flyingwing-polars.pngBuilding on this, the influence of geometric sweep was investigated, showing that realistic sweep values do not provide sufficient stability for the baseline configuration, with only non-physical geometries yielding stable behaviour.
Finally, wing twist was introduced as a design variable, demonstrating that a negative twist of approximately −5° enables stable flight conditions, satisfying all stability criteria within a defined angle-of-attack range.